Mucociliary clearance of foreign particulates from the tracheobronchial tree is an important defense mechanism against inhaled insoluble particulate matter. A failure of this system not only decreases resistance to pulmonary infection but also results in an increased lung burden of carcinogenic matter. Only a rudimentary knowledge of the functioning of this system exists. The present proposal is to investigate the role of the cholinergic nervous system in regulating mucociliary transport. Anatomical studies reveal a dense cholinergic supply to the bronchi. Goblet cells apparently are not innervated, but acinar glands appear to be innervated. Respiratory tract fluid is increased by vagal stimulation and parasympathomimetic agents. My present hypothesis is that the parasympathetic nervous system is involved in the regulation of water secretion into the airway lumen. This affects the visco-elastic properties of the mucous blanket, and, thereby, affects mucociliary transport. My second hypothesis is that this secretion occurs by an actively transported ionic flux. I have developed a new roentgenographic method to study both the pattern and rate of mucociliary transport in living animals. This method uses small tantalum markers. With this technique I will study the effect of the parasympathetic stimulation and blockade on mucociliary transport. I will also measure potential difference, ionic fluxes, and water movement across in vitro tracheal epithelium preparations. Additionally, I will investigate the affects of parasympathomimetic and parasympatholytic agents on these parameters. Subsequent studies will investigate the affects of the sympathetic nervous system.